Neonatal hypoxic-ischemic (HI) brain injury results in devastating, life-long disability for the affected children. At present, hypothermia is the only treatment for neonatal HI and it is incompletely effective. 45% of treated infants still die or sustain severe neurodevelopmental disability following HI. Designing safe, effective, mechanistically novel adjuvant therapies is the highest priority in this field of research. In concert, there is a need to develop mechanistically-based, reliable biomarkers to track novel therapies and measure their efficacy. Our identification of programmed necrosis as a mechanism of injury in neonatal HI provides an opportunity to identify novel therapies. That programmed necrosis may be operative in neonatal HI is clinically compelling. Programmed necrosis, unlike classical necrosis, is regulated, treatable, and is well understood in vitro. How and whether hypothermia acts to inhibit programmed necrosis is unknown and very important to the successful development of adjuvant therapies for neonatal HI. The in vivo neural target of hypothermia and programmed necrosis inhibitors is also a gap in our knowledge. Effects of hypothermia on neurons are best known. Little is known about the effects of hypothermia on glia and nothing is known about the effects of programmed necrosis inhibitors. Glia, oligodendroglia and astrocytes, clearly contribute to the overall encephalopathy resulting from neonatal HI. Astrocytes, in particular, may play a pivotal role in initiation of and protection from HI by both hypothermia and programmed necrosis inhibitors. Because of their possible involvement in the initiation and response to HI injury and treatment, astrocytic release of glial fibrillary acid proein (GFAP) may be the reliable, regionally specific, mechanistically-based biomarker that we seek for neonatal HI brain injury. In this proposal, we will use an established model of neonatal HI and hypothermia address each of these research priorities and areas of knowledge gap. We will test the hypothesis that hypothermia provides neuroprotection following neonatal HI by interrupting programmed necrosis. Subsequently, using data from these experiments we will test combinations of hypothermia, anti-programmed necrosis and anti-apoptosis treatments for treatment of neonatal HI and GFAP as an experimental biomarker. In doing so we will forge new pathways in neonatal brain injury research These experiments address critical, timely, and highly relevant issues in neonatal brain injury.